From Atkins to The Z Diet, there are hundreds of weight loss programmes to choose from if you're trying to slim down.

But as one nutritionist has revealed, some of the most well-known and trendiest diets could actually pose a danger to your health.

Registered nutritionist Rhiannon Lambert has unveiled the fad diets that you should never follow if you want to stay healthy, from the popular juice cleanse to becoming a vegan on a whim.

Juice cleanse

Any suggestion that the human body can be detoxed with a juice cleanse is incorrect. We are naturally designed to remove toxins using our liver and kidneys - a juice cleanse won't perform such a detox.


Those who promote juicing often claim that drinking juice is better than eating whole fruits and vegetables because removing fibre makes nutrients easier to absorb. However, there is no scientific research to support this claim.

Antioxidants are often bound to the fibre in fruit and vegetables and countless research studies suggest that the lack of fibre in juices significantly reduces any supposed health benefits.

Consuming well under 1000 calories per day from juices will likely result in a stark calorie deficit and weight-loss will be inevitable. But this is extremely difficult to sustain for more than a few days and while a juice diet may help initially with slimming, any severe calorie restriction can slow down your metabolism long-term.

Juices should not be used as meal replacements. They do not contain sufficient protein nor healthy fat - both of which are required by the body. In fact, drinking juice over a long period of time could increase the risk of metabolic syndrome, liver damage and even obesity.


At this time of year, many people try veganism to become healthier and lose weight. But only by safely applying a vegan diet will you avoid deficiency in key nutrients.

There are some nutrients that can only be obtained from plants such as vitamin C, and others that can only be obtained from animal sources such as Vitamin B12, which is involved in the function of every cell in the body and brain.

As it isn't found in any non-animal product (except algae), studies suggest vegans are more often than not deficient in this critical nutrient. Other nutrients often forgotten in a vegan diet include vitamin D, omega-3 and iron.

Protein is of course vital for muscle and bone health but also for cells affecting our skin and hair. With about 20 per cent of the human body made up of protein, it's important to get an adequate amount from your diet every single day. Thankfully, there are plenty of delicious, protein-rich plant-based foods to consider incorporating into your diet, including tofu, lentils, quinoa, hemp, chia and beans.

Alkaline diet

The human body regulates its own acidity levels, regardless of what you eat and drink. Photo / Getty
The human body regulates its own acidity levels, regardless of what you eat and drink. Photo / Getty

This weight loss scheme is based on the claim that modern diets cause our body to produce too much acid, which is then turned into fat, leading to weight gain. High acidity levels have also been blamed on conditions such as arthritis, osteoporosis, tiredness, and kidney and liver disorders.

An alkaline diet reduces the number of acid-producing foods you eat, such as meat, grains, refined sugar, dairy, caffeine, alcohol and processed foods, in favour of alkaline foods. Ultimately, the diet will consist of a great deal of fruit and vegetables and a small amount of protein.

While the advice to cut back on processed foods, alcohol, caffeine and refined sugar is good, any weight loss associated with this diet is largely down to the fact these unhealthy foods have been cut out, rather than anything to do with acid and alkaline.

The human body regulates its own acidity levels, regardless of what you eat and drink.
Unlike so many other diets, the alkaline diet is not unhealthy, but its claims are simply not supported by science and human physiology.

Meal replacements

Meal replacement schemes such as the Cambridge Diet is a popular one with people looking for rapid weight loss as it relies on a range of meal-replacement products.
The idea is to restrict calories by eating a range of bars, soups, and shakes, as well as having a few low-calorie meals.

Like with any calorie-restricting diet, weight loss can be dramatic. Despite some products being fortified with vitamins and minerals to ensure nutrition isn't lost, the very mindset of giving up normal meals and swapping them for a snack bar or a shake can be boring, socially isolating and difficult to maintain long-term.

And while fortified products are a welcome addition to any restrictive diet, the inclusion of sugar and artificial chemicals is definitely not, with studies suggesting that they will limit any health benefits from vitamins and minerals.

A blackcurrent and apple shake, for example, contains 44.1g of sugar per 100g - significantly above your recommended daily intake.

Low-calorie meal plans

Low-calorie weight loss programmes are based on your Body Mass Index (BMI) score, which will dictate how many meals a day you have.

This diet does advise you to see a GP before you start and can fit into a busy schedule - but it has many drawbacks. Restricting carbohydrates and fibre will result in side effects such as tiredness, dizziness, and constipation, making this plan unsustainable long-term.

It could also impact on your mental well-being. Without any allowance for spontaneous eating out, they are unsustainable as diet plans.

Any low-calorie diet that involves eating 1,000 calories a day or less should not be followed for more than 12 continuous weeks and should require professional medical supervision.

Low-fat meal plans

These diets encourage the swapping of high-fat foods for low-fat foods which are naturally filling. But this idea is out-dated, with healthy fats now considered a crucial element in our meals.

On these diets, some items are considered "free foods" which can be eaten in unlimited amounts including fruit, vegetables, pasta, meat, fish and eggs. No calorie counting is involved and no foods are banned, and it's said you could lose one or two pounds a week.

But without any education surrounding portion sizes and nutritional intake, many will find it difficult to understand what to do when the programme ends and struggle to keep the weight off long-term.

Regularly weighing in as part of a group can also be psychologically damaging, and eating out can be a challenge, as you have to watch your food combinations.

There would also be a temptation to fill up on "free foods" such as processed meats without any concern for the salt, sugar and other unhealthy additives contained in them.

With many carbohydrates restricted, these diets will only worsen some people's obsessive fear of supposed "bad foods".